The HRM sensors are too big and need too big batteries. The popular ones even shun bluetooth to preserve battery though this feels more possible to me. https:/

The HRM sensors are too big and need too big batteries. The popular ones even shun bluetooth to preserve battery though this feels more possible to me. https://www.crowdsupply.com/oddly-specific-objects/sensor-watch-pro https://www.crowdsupply.com/oddly-specific-objects/sensor-wa...